It's probably a reference to the coin-flipping gangster trope from the 1930s.
The old car and the tough demeanor of the dolphin flipping a coin is most likely a reference to the coin-flipping gangster/tough-guy trope that was originated by George Raft in the 1932 film Scarface. This trope was widely used during the 1930s and 1940s, so it is difficult to say if there is a specific film that is being parodied, or just the trope.
The fact that the 1932 Ford is yellow could be a reference to American Grafitti
In the era of black and white movies when the coin-flipping trope was at its height, you would not have been able to tell if a car was yellow, and the vast majority of them were dark-toned. However, a yellow 1932 Ford did appear in the 1973 film American Grafitti, so it is possibly a reference. That said, there is nothing else about the scene or the episode that in any other way recalls American Grafitti, so if it is a reference, it is an oblique one that stands alone.